This invention relates to microwave ovens and specifically with apparatus and methods employed to improve the distribution of energy in the oven.
It is well-known to use a rotatable stirrer in the path of microwave energy to vary energy standing wave patterns and improve energy distribution patterns. Such stirrers may be located in the waveguide, in the cooking cavity, or in a transition zone between the waveguide and the cooking cavity commonly referred to as a feed box.
Stirrers are most frequently motor driven at fairly slow speeds of rotation on the order of 40-65 RPM. Substantially higher speeds of rotation have been found to be less effective in evenly dispersing microwave energy in a cavity than those of the slower speeds indicated.
Several workers in the field have suggested motorless stirrers driven by the passage of air across the blades, the air being derived from that provided for oven component cooling. While air driven stirrers can represent a more economical arrangement than a motor driven stirrer, the air driven variety has been far less widely used because of problems in controlling rotation and arriving at the proper balance between the relative locations of the stirrer and the air source on the one hand and the proper speed of rotation on the other. The more remote the stirrer is located from the cooling air source the greater the requirement to provide a stirrer mechanism having very low rotational friction losses, hence requiring less driving power.